I took one a day of this product for 8 months. It raised my blood level from 29 ng/ml to 39 ng/ml. I increased to 2/day (10,000 IU total). In 2 months my blood level has come up to 46 ng/ml. I want to get to about 80 ng/ml.

I'm sure it's a good product, but the tablet shape/size is difficult. I take lots of pills, so it's not that I have a difficult time with swallowing pills. I have some larger tablets that are easier to swallow--it apparently has to do with the shape.